1. Field of the Invention
The present invention relates to improvements in electrophotographic devices in general, and more particularly to improvements in electrophotographic devices which can obtain images of good quality by making the potential at the surface the photosensitive body substantially uniform at the termination of copying, by adjusting optical systems, by making uniform exposures, and the like.
2. Description of the Prior Art
Of the two typical types of electrophotography, one type uses a photosensitive paper and the other type uses a conventional paper onto which is transferred an image which has been formed on a photosensitive layer consisting mainly of CdS, Zinc oxide and the like.
This invention relates to the latter type. A photosensitive member having a photoconductive layer consisting of CdS, Zinc oxide, Se, etc. and a conductive base of Al, etc. is disposed around the periphery of a rotatable drum. This drum type photosensitive member, similar to a belt type photosensitive member, is disposed at the center portion of the electrophotographic device and disposed around this photosensitive member are a positive or negative corona charger for uniformly charging said photoconductive layer (either positive or negative as determined according, for example, to the P type or N type nature of the photoconductive layer), an optical system, a corona discharger (positive or negative) for separating a transfer paper from the drum or a corona charger for improving the transfer of the image are disposed.
In such a device as mentioned above, when all processes necessary for copying are repeated for obtaining the necessary numbers of copies, the rotation of the drum is stopped simultaneously with the cutting off of the power source for the chargers, a uniform influence is not effected by the corona charger with the provision of said chargers in a spaced relation in the periphery of the drum. As a result, charged and uncharged portions are produced and if permitted to remain, the photoconductive layer is differently affected. Therefore, at the time of successive copying, a charge is not imparted uniformly to the photoconductive layer which often produces an uneven image and thus one is not able to obtain an image of the best quality.
The invention eliminates the aforementioned disadvantages. An uneven or dim image is sometimes caused by a slight error in length of the light path of an optical system (from the original to be exposed to a photosensitive body) between a device in design and an actual device. Further, it is difficult to uniformly illuminate the original so that there is sometimes produced a difference of exposure between the central part and the peripheral part of the light image.
The present invention eliminates the disadvantages noted above.